The nature of Galactic interstellar extinction is tested using reddening line parameters for several fields in conjunction with equivalent widths $W(lambda4430)$ for the diffuse interstellar band at $4430$ AA. The Cardelli et al.$;$relations [29] at
infrared, optical, and ultraviolet wavelengths are inconsistent with the newly-derived quadratic variation of $R_V({rm observed})$ on reddening slope $X$. A minimum of $R_V=2.82pm0.06$ exists for $X=0.83pm0.10$, and is argued to represent true Galactic extinction described by $A(lambda)propto lambda^{-1.375}$. It matches expectations for a new description of extinction in the infrared, optical, and ultraviolet by Zagury [32]. Additional consequences, reddened stars with no 2175 AA$;$feature and a correlation of normalized $lambda4430$ absorption with $X$, are not predicted by the Cardelli et al.$;$relation [29]. Known variations in $X$ from 0.62 to 0.83, and corresponding variations in $R_V({rm observed})$ from 4.0 to 2.8, presumably result from forward-scattered starlight in the ultraviolet contaminating optical light of stars affected by dust extinction. A new understanding of the true nature of interstellar extinction is important for establishing an accurate picture of the extragalactic distance scale, which in turn is related to our understanding of the nature of the Universe.
The parameters for the newly-discovered open cluster Alessi 95 are established on the basis of available photometric and spectroscopic data, in conjunction with new observations. Colour excesses for spectroscopically-observed B and A-type stars near
SU Cas follow a reddening relation described by E(U-B)/E(B-V)=0.83+0.02*E(B-V), implying a value of R=Av/E(B-V)~2.8 for the associated dust. Alessi 95 has a mean reddening of E(B-V)_(B0)=0.35+-0.02 s.e., an intrinsic distance modulus of Vo-Mv=8.16+-0.04 s.e. (+-0.21 s.d.), d=429+-8 pc, and an estimated age of 10^8.2 yr from ZAMS fitting of available UBV, CCD BV, NOMAD, and 2MASS JHKs observations of cluster stars. SU Cas is a likely cluster member, with an inferred space reddening of E(B-V)=0.33+-0.02 and a luminosity of <Mv>=-3.15+-0.07 s.e., consistent with overtone pulsation (P_FM=2.75 d), as also implied by the Cepheids light curve parameters, rate of period increase, and Hipparcos parallaxes for cluster stars. There is excellent agreement of the distance estimates for SU Cas inferred from cluster ZAMS fitting, its pulsation parallax derived from the infrared surface brightness technique, and Hipparcos parallaxes, which all agree to within a few percent.
A VI Wesenheit diagram featuring SX Phoenicis, delta Scuti, RR Lyrae, type II and classical Cepheid variables is calibrated by means of geometric-based distances inferred from HST, Hipparcos, and VLBA observations (n=30). The distance to a target pop
ulation follows from the offset between the observed Wesenheit magnitudes and the calibrated template. The method is evaluated by ascertaining the distance moduli for the LMC (mu_0=18.43+-0.03 se) and the globular clusters omega Cen, M54, M13, M3, and M15. The results agree with estimates cited in the literature, although a nearer distance to M13 is favoured (pending confirmation of the datas photometric zero-point) and observations of variables near the core of M15 suffer from photometric contamination. The calibrated LMC data is subsequently added to the Wesenheit template since that galaxy exhibits precise OGLE photometry for innumerable variables of differing classes, that includes recent observations for delta Scuti variables indicating the stars follow a steeper VI Wesenheit function than classical Cepheids pulsating in the fundamental mode. VI photometry for the calibrators is tabulated to facilitate further research, and includes new observations acquired via the AAVSOs robotic telescope network (e.g., VY Pyx: <V>=7.25 and <V>-<I>=0.67). The approach outlined here supersedes the lead authors prior first-order effort to unify variables of the instability strip in order to establish reliable distances.
In their study Bottke et al. (2007) suggest that a member of the Baptistina asteroid family was the probable source of the K/T impactor which ended the reign of the Dinosaurs 65 Myr ago. Knowledge of the physical and material properties pertaining to
the Baptistina asteroid family are, however, not well constrained. In an effort to begin addressing the situation, data from an international collaboration of observatories were synthesized to determine the rotational period of the familys largest member, asteroid 298 Baptistina (P_r = 16.23+-0.02 hrs). Discussed here are aspects of the terrestrial impact delivery system, implications arising from the new constraints, and prospects for future work.
